Methods and apparatuses for reference signal transmission and receiving

ABSTRACT

Embodiments relate to reference signal transmission and receiving in a wireless communication system A common reference signal sequence is generated based on a frequency range configuration at network side, the common reference signal sequence being shared by at least some of terminal devices respectively allocated with their own reference signal transmission configurations. The common reference signal sequence and sequence configuration information is transmitted to a terminal device, the sequence configuration information indicating a parameter by which a reference signal sequence transmitted for the terminal device can be obtained. A reference signal sequence solution with a low complexity is proposed for the wireless communication system with dynamic bandwidth allocation and/or configurable reference signal pattern, wherein only one common reference signal sequence is generated and shared by at least some of terminal devices, irrespective of reference signal transmission configurations like bandwidth allocation and/or reference signal pattern configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 16/993,798 filed on Aug. 14, 2020, which is acontinuation application of U.S. patent application Ser. No. 16/235,044filed on Dec. 28, 2018, which issued as U.S. Pat. No. 10,790,951, whichis a National Stage Entry of international applicationPCT/CN2017/070302, filed on Jan. 5, 2017, the disclosures of all ofwhich are incorporated in their entirety by reference herein.

FIELD OF THE INVENTION

The non-limiting and exemplary embodiments of the present disclosuregenerally relate to the field of wireless communication techniques, andmore particularly relate to methods and apparatuses for reference signaltransmission and receiving in a wireless communication system.

BACKGROUND OF THE INVENTION

New radio access system, which is also called as NR system or network,is the next generation communication system. In Radio Access Network(RAN) #71 meeting for the third generation Partnership Project (3GPP)working group, study of the NR system was approved. The NR system willconsider frequency ranging up to 100 Ghz with an object of a singletechnical framework addressing all usage scenarios, requirements anddeployment scenarios defined in Technical Report TR 38.913, whichincludes requirements such as enhanced mobile broadband, massivemachine-type communications, ultra reliable and low latencycommunications.

Initial work of the study item should allocate high priority on gaininga common understanding on what is required in terms of radio protocolstructure and architecture with focus on progressing in the followingareas:

-   -   Fundamental physical layer signal structure for new RAT    -   Waveform based on OFDM, with potential support of non-orthogonal        waveform and multiple access    -   FFS: other waveforms if they demonstrate justifiable gain    -   Basic frame structure(s)    -   Channel coding scheme(s)

In addition, it is also required to study and identify the technicalfeatures necessary to enable the new radio access, including:

-   -   Efficient multiplexing of traffic for different services and use        cases on the same contiguous block of spectrum

Furthermore, dynamic/flexible bandwidth allocation and configurable RSpattern (including density) were also agreed on in RAN1.

The dynamic/flexible bandwidth allocation means that a dynamic/flexibleand UE specific bandwidth allocation shall be supported in NR. Thus, insuch a case, UE will not know the whole system bandwidth at the networkside, different UE might need different reference signal sequences andit is impossible to generate a shared RS sequence for UEs by using theexisting RS sequence generation solution. On the other hand, the RSpattern can also be configurable (e.g. configurable density in time/orfrequency domain), therefore the legacy RS sequence cannot satisfyrequirements for different patterns, especially for multi-userscheduling.

SUMMARY OF THE INVENTION

In the present disclosure, there is provided a new solution forreference signal transmission and receiving in a wireless communicationsystem, to mitigate or at least alleviate at least part of the issues inthe prior art.

According to a first aspect of the present disclosure, there is provideda method of reference signal transmission in a wireless communicationsystem. The method comprises generating, based on a frequency rangeconfiguration at network side, a common reference signal sequence sharedby at least some of terminal devices respectively allocated with theirown reference signal transmission configurations; and transmitting thecommon reference signal sequence and sequence configuration informationto a terminal device, the sequence configuration information indicatinga parameter by which an initial reference signal sequence transmittedfor the terminal device can be obtained.

According to a second aspect of the present disclosure, there isprovided a method of reference signal receiving in a wirelesscommunication system. The method comprises receiving a reference signalsequence transmitted from network side and sequence configurationinformation indicating a parameter by which an initial reference signalsequence transmitted for the terminal device can be obtained; andobtaining the initial reference signal sequence for the terminal devicebased on the sequence configuration information.

According to a third aspect of the present disclosure, there is providedan apparatus of reference signal transmission in a wirelesscommunication system. The apparatus comprises: a reference signalgeneration module and a sequence and information transmission module.The reference signal generation module is configured to generate, basedon a frequency range configuration at network side, a common referencesignal sequence shared by at least some of terminal devices respectivelyallocated with their own reference signal transmission configurations.The sequence and information transmission module is configured totransmit the common reference signal sequence and sequence configurationinformation to a terminal device, the sequence configuration informationindicating a parameter by which an initial reference signal sequencetransmitted for the terminal device can be obtained.

According to a fourth aspect of the present disclosure, there isprovided an apparatus of reference signal receiving in a wirelesscommunication system. The apparatus comprises: a sequence and signalreceiving module and a sequence obtainment module. The sequence andsignal receiving module is configured to receive a reference signalsequence transmitted from network side and sequence configurationinformation indicating a parameter by which an initial reference signalsequence transmitted for the terminal device can be obtained. Thesequence obtainment module is configured to obtain the initial referencesignal sequence for the terminal device based on the sequenceconfiguration information.

According to a fifth aspect of the present disclosure, there is provideda computer-readable storage media with computer program code embodiedthereon, the computer program code configured to, when executed, causean apparatus to perform actions in the method according to anyembodiment in the first aspect.

According to a sixth aspect of the present disclosure, there is provideda computer-readable storage media with computer program code embodiedthereon, the computer program code configured to, when executed, causean apparatus to perform actions in the method according to anyembodiment in the second aspect.

According to a seventh aspect of the present disclosure, there isprovided a computer program product comprising a computer-readablestorage media according to the fifth aspect.

According to an eighth aspect of the present disclosure, there isprovided a computer program product comprising a computer-readablestorage media according to the sixth aspect.

With embodiments of the present disclosure, a reference signal sequencesolution with a low complexity is proposed for the wirelesscommunication system (especially for new radio access system) withdynamic bandwidth allocation and/or configurable reference signalpattern, wherein one common reference signal sequence can be generatedand shared by at least some of terminal devices, irrespective ofreference signal transmission configurations like bandwidth allocationand/or reference signal pattern configurations. Thus, it is possible toperform RS measurement and multi-user scheduling for UE even if they areconfigured different bandwidth allocation and/or configurable referencesignal pattern. In addition, it can achieve a better interferencecancellation since reference signals from interfering cells will be easyto be obtained. Moreover, it only needs terminal devices to generate few(for example, only one) reference signal sequence for different bandallocations and/or RS pattern configurations, which means a less complexsolution.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure will become moreapparent through detailed explanation on the embodiments as illustratedin the embodiments with reference to the accompanying drawings,throughout which like reference numbers represent same or similarcomponents and wherein:

FIG. 1 schematically illustrates system bandwidth configurations in theLTE system;

FIG. 2 schematically illustrates example potential issues associatedwith dynamic bandwidth allocation in the NR system;

FIG. 3 schematically illustrates example potential issues associatedwith configurable RS pattern in the NR system;

FIG. 4 schematically illustrates a flow chart of a method for referencesignal transmission according to an example embodiment of the presentdisclosure;

FIG. 5 schematically illustrates a common RS sequence and RS sequencesfor respective UE with different frequency band allocations according toan example embodiment of the present disclosure;

FIG. 6 schematically illustrates an example common RS sequencegeneration according to another embodiment of the present disclosure;

FIG. 7 schematically illustrates an example common RS sequencegeneration with a fixed index according to a further embodiment of thepresent disclosure;

FIG. 8 schematically illustrates an example common RS sequencegeneration with a fixed index according to a still further embodiment ofthe present disclosure;

FIG. 9 schematically illustrates an example common RS sequence for UEwith configurable RS patterns according to a still further embodiment ofthe present disclosure;

FIG. 10 schematically illustrates a common RS sequence and RS sequencesfor respective UE with different RS densities according to an embodimentof the present disclosure;

FIG. 11 schematically illustrates a common RS sequence and RS sequencesfor respective UE with different RS configurations in time domainaccording to another example embodiment of the present disclosure;

FIG. 12 schematically illustrates a common RS sequence and RS sequencesfor respective UE with different band allocations in frequency domainand different RS configurations in time domain according to anotherexample embodiment of the present disclosure;

FIGS. 13 to 15 schematically illustrates different varying modes ofmodulated symbols in the RS sequence according to embodiments of thepresent disclosure;

FIGS. 16A and 16B schematically illustrates common RS sequencegeneration for symbols with different densities according to anembodiment of the present disclosure;

FIG. 17 schematically illustrates a flow chart of a method for referencesignal receiving according to an embodiment of the present disclosure;

FIG. 18 schematically illustrates a block diagram of an apparatus forreference signal transmission according to an embodiment of the presentdisclosure;

FIG. 19 schematically illustrates a block diagram of an apparatus forreference signal receiving according to an embodiment of the presentdisclosure; and

FIG. 20 further illustrates a simplified block diagram of an apparatus2010 that may be embodied as or comprised in a serving node like a basestation in a wireless network and an apparatus 2020 that may be embodiedas or comprised in a terminal device like UE as described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, the solution as provided in the present disclosure will bedescribed in details through embodiments with reference to theaccompanying drawings. It should be appreciated that these embodimentsare presented only to enable those skilled in the art to betterunderstand and implement the present disclosure, not intended to limitthe scope of the present disclosure in any manner.

In the accompanying drawings, various embodiments of the presentdisclosure are illustrated in block diagrams, flow charts and otherdiagrams. Each block in the flowcharts or blocks may represent a module,a program, or a part of code, which contains one or more executableinstructions for performing specified logic functions, and in thepresent disclosure, a dispensable block is illustrated in a dotted line.Besides, although these blocks are illustrated in particular sequencesfor performing the steps of the methods, as a matter of fact, they maynot necessarily be performed strictly according to the illustratedsequence. For example, they might be performed in reverse sequence orsimultaneously, which is dependent on natures of respective operations.It should also be noted that block diagrams and/or each block in theflowcharts and a combination of thereof may be implemented by adedicated hardware-based system for performing specifiedfunctions/operations or by a combination of dedicated hardware andcomputer instructions.

Generally, all terms used in the claims are to be interpreted accordingto their ordinary meaning in the technical field, unless explicitlydefined otherwise herein. All references to “a/an/the/said [element,device, component, means, step, etc.]” are to be interpreted openly asreferring to at least one instance of said element, device, component,means, unit, step, etc., without excluding a plurality of such devices,components, means, units, steps, etc., unless explicitly statedotherwise. Besides, the indefinite article “a/an” as used herein doesnot exclude a plurality of such steps, units, modules, devices, andobjects, and etc.

Additionally, in a context of the present disclosure, a user equipment(UE) may refer to a terminal, a Mobile Terminal (MT), a subscriberstation, a portable subscriber station, Mobile Station (MS), or anAccess Terminal (AT), and some or all of the functions of the UE, theterminal, the MT, the SS, the portable subscriber station, the MS, orthe AT may be included. Furthermore, in the context of the presentdisclosure, the term “BS” may represent, e.g., a node B (NodeB or NB),an evolved NodeB (eNodeB or eNB), gNB (Node B in NR), a radio header(RH), a remote radio head (RRH), a relay, or a low power node such as afemto, a pico, and so on.

Hereinafter, the Channel State Information-Reference Signal (CSI-RS)sequence generation in LTE system will be first described to facilitatethe understanding of embodiment of the present disclosure.

According to the CSI-RS generation in LTE, the reference-signal sequencer_(l,n) _(s) (m) is defined by:

${{r_{l,n_{s}}(m)} = {{{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)\mspace{31mu} m}} = 0}},1,\ldots\mspace{14mu},{N_{RB}^{\max,{DL}} - 1}$

where n_(s) is the slot number within a radio frame and/is the OFDM'ssymbol number within the slot; c(i) is a pseudo-random sequencegenerated by a pseudo-random sequence generator, which shall beinitialized with

C _(init)=2¹⁰·(7·(n _(s)+1)+l+1)·2·N _(ID) ^(CSI)+1+2·N _(ID) ^(CSI) +N_(CP)

at the start of each OFDM symbol where

$N_{CP} = \left\{ \begin{matrix}1 & {{for}\mspace{14mu}{normal}\mspace{14mu}{CP}} \\0 & {{for}\mspace{14mu}{extended}\mspace{14mu}{CP}}\end{matrix} \right.$

and wherein the quantity N_(ID) ^(CSI) equals to N_(ID) ^(cell) unlessit is configured by higher layers.

In subframes configured for CSI reference signal transmission, thereference signal sequence r_(l,n) _(s) (m) shall be mapped tocomplex-valued modulation symbols α_(k,l) ^((p)) used as referencesymbols on antenna port p according to

$a_{k,l}^{(p)} = {{w_{l^{''}} \cdot {r_{l,n_{s}}\left( m^{\prime} \right)}}\mspace{31mu}\begin{matrix}{{m = 0},1,\ldots\mspace{14mu},\ {N_{RB}^{DL} - 1}} \\{{m’} = {m + \left\lfloor \frac{N_{RB}^{\max,{DL}} - N_{RB}^{DL}}{2} \right\rfloor}}\end{matrix}}$

Thus, it is clear that the CSI-RS sequence is generated with a fixedmaximum length N_(RB) ^(max,DL) and the configured length N_(RB) ^(DL).The configured length N_(RB) ^(DL) is associated with configuration ofsystem bandwidth at the network.

The index for CSI-RS sequence generation is known to UE, the N_(RB)^(max,DL) is fixed to 110 and the N_(RB) ^(DL) can be obtained fromphysical broadcast channel (PBCH), and the CSI-RS is full band one.Thus, the generated CSI-RS can be shared by all UEs in the cell.

Therefore, in the LTE system, the CSI-RS sequence is generated with afixed maximum length, and for each of six different configurations ofsystem bandwidth as illustrated FIG. 1, which have the same centralfrequency, the generated CSI-RS sequence will be fixed. Thus, for thesame cell ID, the CSI-RS sequence is common for all UEs in the cell.

However, things will be different in the NR system. As mentionedhereinbefore, the dynamic/flexible bandwidth allocation will besupported in NR system and thus the UE will not know the whole systembandwidth at the network side. In addition, different UE might needdifferent reference signal sequences since they might be allocated withdifferent frequency bands. With the existing RS sequence generationsolution, it is impossible to generate a single RS sequence which can beshared for UE.

FIG. 2 illustrates example potential issues associated with dynamicbandwidth allocation in the NR system. As illustrated in FIG. 2, thereare three different UE, i.e. UE1, UE2, and UE3, which are located in thesame cell but configured, for scheduling/measurement, with UE-specificfrequency bands each of which is only a part of the whole system bandconfigured at network side. The frequency bands for different UE can beseparated, or partially/fully overlapped, as illustrated in FIG. 2. FromUE's perspective, its whole bandwidth depends on the RF capability, andit's not mandated to know the system bandwidth at network side and thusthe band allocation should be transparent.

In such a case, RS configuration with dynamic band allocation mightresult in some issues. For example, for the cell or beam specific RS, itshall be common or shared by a group of UEs, like RS for CSImeasurement. In addition, considering multi-user MIMO scheduling, thedemodulation RS should also be unified for orthogonally co-scheduling.Even for the different sequences of RS for quasi-orthogonal or forinter/intra-cell interference management, the RS sequence should be ableto be known for other UEs for advanced interference cancellation. Inthose cases, RS configuration with the dynamic band allocation, whichwill not enable RS sharing, will be a problem.

In addition, in the NR system, the UE can be configured with aUE-specific RS pattern (e.g. UE-specific RS density) in time/frequencydomain. In such a case, it is also impossible to share a common RS withthe existing RS generation solution. However, a common RS generationmight be also beneficial in many cases, especially when RS pattern isdynamically changed, since the UE can abstract the needed RS from acommon sequence. Moreover, the common sequence can facilitate multi-userscheduling.

As illustrated in FIG. 3, if UE generates their RS sequences separately,the received signals on REs are Y₁ and Y₂, which will respectively berepresented as follows:

Y ₁ =H ₁ *R ₀(n+2)+H ₂ *R ₀(n+1)

Y ₂ =H ₁ *R ₁(n+2)−H ₂ *R ₁(n+ ¹)

R ₀(n+2)≠R ₁(n+2)≠R ₀(n+1)≠R ₁(n+1).

However, in such a case, as illustrated in FIG. 3, for different RSpatterns, the orthogonality cannot be guaranteed, which means thatchannels H1 and H2 for each UE cannot be estimated. Moreover, each UEmight cause interference to others, and it's unable for advanced UE tosubtract interference from other UEs. Thus, the legacy RS sequencegeneration cannot satisfy requirements for different RS patterns aswell, especially for multi-user scheduling.

In view of the above, in the present disclosure, there is proposed acommon RS sequence design solution which is irrespective of UE bandwidthor RS pattern configuration. By means of the common RS sequence design,a group of UE with their own RS transmission configurations can share acommon RS sequence, such as those RS for measurement and multi-usescheduling. In addition, it may achieve a better interferencecancellation as the RS from an interference cell is easy to be obtained.Moreover, UE only needs to generate a few of sequence (e.g. only one)for different band allocation/pattern configuration, which means a lesscomplexity in RS sequence generation.

Hereinafter, reference will be made to the accompanying drawings todescribe the solution for reference signal transmission and receiving asproposed herein. However, it shall be noted that these description aremade only for illustration purposes and the present disclosure is notlimited thereto.

Reference is first made to FIG. 4, which schematically illustrates aflow chart of a method 400 of reference signal transmission in awireless communication system according to an embodiment of the presentdisclosure. The method 400 can be performed at a serving node, forexample a BS, like a node B (NodeB or NB).

As illustrated in FIG. 4, first in step 401, a common reference signalsequence is generated based on a frequency range configuration atnetwork side, the common reference signal can be shared by at least someof terminal devices respectively allocated with their own referencesignal transmission configurations.

In an embodiment of the present disclosure, a common reference signalsequence is generated based on system bandwidth at network side. Inother word, the length of the common reference signal sequence isdetermined based on at least the whole system bandwidth at network side.

As illustrated in FIG. 5, the common reference signal sequence R_i iscomprised of R_0, R_1, R_2, . . . , R_M_2, R_M_1, wherein M is thelength of the reference signal R_i and is related to at least the systembandwidth at network side. In addition, it may be also further relatedto the minimum subcarrier space (SCS).

The sequence R_i may be defined by a pseudo-random sequence which can beinitialized by the pseudo-random sequence generator with an initialvalue C_init. The initial value C_init can be calculated with parametersrelated to at least one of slots index n_(s), symbol index l, cell_IDN^(ID), UE_ID U^(ID), CP type N_(CP), index of SCS configurationN_(SCS), link type N_(link_type) and etc. In an example embodiment ofthe present disclosure, the C_init can be determined as follows:

C_init=a ₀ ·n _(s) +a ₁ ·l+a ₂ ·N ^(ID) +a ₃ ·U ^(ID) +a ₄ ·N _(CP) +a ₅·N _(SCS) +a ₆ ·N _(link_type)

where a_(i) is coefficient for each factor, i=0, 1, . . . , the numberof parameters, N_(SCS) is a parameter of subcarrier space configuration,and the value of N_(SCS) can be selected from a set of values, eachvalue corresponding to a subcarrier space; N_(link_type) is a parameterof link type which indicates the initial value is for downlink, uplinkor sidelink. It shall be noticed that for the at least some of terminaldevice, they will be allocated with the same U^(ID) and thus they canshare the generated RS sequence.

In an embodiment of the present disclosure, the following table can beused for indicating the subcarrier space configurations.

TABLE 1 Example subcarrier space configurations N_(SCS) Subcarrier space0   15 kHz 1   30 kHz 2   60 kHz 3  120 kHz 4  240 kHz 5  480 kHz 6 3.75kHz if supported . . . . . .

Regarding the link type parameter N_(link_type), the following table canbe used as a way to indicate the link type.

TABLE 2 Example link type indications N_(link)_type Link type 0 Downlink1 Uplink

For the downlink or uplink, the RS sequence can be symmetric, and thesequence can be generated with different initial values.

Thus, with the common RS sequence with a length M as illustrated in FIG.5, for different UE with different bandwidth configurations, for examplethose configured with different frequency ranges/or positions in thesystem frequency band, their respective RS sequences will start fromdifferent indices of the common RS sequence and have different lengths.As illustrated, the RS sequence for UE 1 may start from i_start_1 (R_3in the common RS sequence) and end at i_end_1 (R_10 in the common RSsequence); the RS sequence for UE 2 may start from i_start_2 (R_i in thecommon RS sequence) and end at i_end_2 (R_M−2 in the common RSsequence); the RS sequence for UE 3 may start from i_start_3 (R_2 in thecommon RS sequence) and end at i_end_3 (R_i+2 in the common RSsequence). In other words, RS sequences for respective UE willcorrespond to their own allocated frequency bands. Herein, the startindex of the RS sequence for UE is also called as the index of the RSsequence for the UE.

Reference is made back to FIG. 4, at step S402, the common referencesignal sequence and sequence configuration information will betransmitted to a terminal device, the sequence configuration informationindicating a parameter by which an initial reference signal sequencetransmitted for the terminal device can be obtained.

The common RS sequence can be transmitted to the at least some ofterminal devices and respective terminal devices will receive RSsequences for themselves at their own allocated bands respectively.However, the terminal devices also needs to know initial modulatedsymbols of the RS sequence (i.e., the initial RS sequence withoutundergoing channels) to, for example, perform channel measurement orco-scheduling. Thus, the sequence configuration information, whichindicates a parameter by which an initial reference signal sequencetransmitted for the terminal device can be obtained, can be transmittedto the terminal device as well. By means of the parameter carried withinthe sequence configuration information, the terminal device may obtainthe RS sequence from a common RS sequence generated in a similar way tothat described at step 401.

In an embodiment of the present disclosure, the sequence configurationinformation may be transmitted to the terminal devices in an explicitaway. For example, the sequence configuration information may comprisesequence position information indicating a position at which thereference signal sequence for the terminal device is located in thecommon reference signal sequence. The sequence position information mayinclude any of:

-   -   1) a start index and an end index of the reference signal        sequence for the terminal device, i.e., i_start_ue, and        i_end_ue;    -   2) a start index and the length of the reference signal sequence        for the terminal device, i.e., i_start_ue and m_ue; and    -   3) an end index and the length of the reference signal sequence        for the terminal device, i.e., i_end_ue and m_ue.

In addition, it can be known that different from the RS generationsolution in LTE the index of the RS sequence for the terminal device isnot corresponding to the index of the frequency band. In such a case, itis also possible to send an offset value relative to the frequencyconfiguration of the terminal device to the terminal device. The offsetvalue indicates the offset of the index of the RS sequence for theterminal device with regard the index of the frequency band allocated tothe terminal device. In another embodiment of the present disclosure, itis also possible to send an offset value relative to a fixed frequencyposition. In such a way, the terminal device can know how to obtain itsRS sequence as well.

In another embodiment of the present disclosure, it may also send thelength M of the common RS sequence to the UE.

In another embodiment of the present disclosure, it is also possible totransmit the sequence configuration information implicitly. In otherword, the sequence configuration information can be implicitly indicatedfrom other parameters. Examples of these parameters may include, but notlimited to boundaries/length of frequency band allocated to the terminaldevice, frequency band configuration of the terminal device, a sequencegeneration initial value for the terminal device.

As described hereinbefore, the RS sequence for the terminal device iscorresponding to its own allocated bandwidth and thus theboundaries/length of frequency band allocated to the terminal device canbe used to indicate the sequence configuration information implicitly.In addition, if a terminal device's band is selected from a predefinedgroup of bands with predetermined indication values, by means of thefrequency band configuration, the terminal device can learn theallocated frequency band from the predetermined value and thus obtainthe sequence configuration information. Besides, it is also possible totransmit to the terminal device a sequence initialization valueC_init_ue, from which the terminal device could generate its RS sequenceby itself. The C_init_ue is specific to the terminal device butoriginated from the C_init for the common RS sequence, and thus it willmake symbols of RS sequence for different terminal devices same at thesame frequency or time position.

It shall be noticed that, although hereinbefore, the present disclosureis described with embodiments wherein the common RS sequence isgenerated based on the system bandwidth at network side, the presentdisclosure is not limited thereto. In an embodiment of the presentdisclosure, the common RS sequence can be generated based on thefrequency band configured for a node serving the terminal device insteadof the whole system bandwidth. It can be appreciated that differentserving nodes may be allocated different frequency bandwidth and in sucha case, it is also possible for the network to generate a common RSsequence corresponding to its allocated frequency bandwidth.

For example, for different frequency range configurations, the startindex for RS sequence generation may be different. However, in such acase, the common reference signal sequence can be generated based on afrequency range covering all possible frequency ranges of the differentfrequency range configurations. in such a case, it will make ensure thatthe RS sequences for different frequency range configurations have thesame value at the same frequency positions.

For example, as illustrated in FIG. 6, there are two different frequencyrange configurations, frequency range 1 and frequency range 2. In otherwords, the two transmission and reception points (TRPs)/cells or twoconfigurations of one cell are configured with different frequencyband/or numerology allocations. If the UE needs to measureinter-TRP/cell interference, the RS sequence should be same in someregion (e.g., for the superposition part). In this case, it is possibleto generate the common sequence from the same starting position idx_rs,which is corresponding to the lower boundary of the two frequencyranges.

For each UE, the index idx_rs for RS generation can be indicated to theUE, and the offset value k with regard to the idx_rs can be alsoindicated to the UE. In such a case, the UE can determine the startindex for its RS sequence as, for example, idx_rs1=idx_rs+k. Oralternatively, the start index idx_b1 for band/numerology allocation forUE, which is independent from idx_rs, can be indicated to the UE. The RSsequence for two different frequency range configurations can beobtained from the common RS sequence generated from idx_rs. The RSsequence parameters (e.g. for serving cell and neighbor cell) can beindicated to the UE. The parameters may include at least one of startingindex, length, ending index, offset value, numerology, etc.

In an embodiment of the present disclosure, the different frequencyrange configurations can have at least one of different subcarrierspacing configurations and different cyclic prefix configurations.

In an embodiment of the present disclosure, a fixed index can be usedfor RS sequence generation for different numerologies. The index can bedetected by UE, e.g. by synchronization signals. In other word, fornumerology in different numerology configurations, the common referencesignal sequence can be generated based on a frequency range covering allpossible frequency range of the numerology; and a fixed index and anoffset value with regard to the fixed index can be used to indicate thesequence configuration information.

FIG. 7 illustrates an example common RS sequence generation with a fixedindex according to an embodiment of the present disclosure. Asillustrated, for different numerology configurations containing forexample three numerologies, for each of numerologies 1, 2, and 3 inthese numerology configurations, the common RS sequence generation canuse the fixed index, i.e., index 1, 2 or 3 respectively. That is to say,a common RS sequence generation is generated based on a frequency rangecovering all possible frequency range of the numerology, and a fixedindex and an offset value are used as the sequence configurationinformation. In such a way, it is possible to keep the reference signalsame in the same frequency position.

FIG. 8 illustrates an example common RS sequence generation with a fixedindex according to another embodiment of the present disclosure. Thesolution is substantially similar to that in FIG. 7 but different inthat the index is fixed at the central position of each frequency range.That is to say, all the frequency ranges have the same central frequencyposition.

In another embodiment of the present disclosure, the index for RSsequence generation for different numerologies can be configured bynetwork.

Hereinafter, the present disclosure is described mainly with referenceto dynamic bandwidth allocation but the present disclosure is notlimited there to. The present disclosure can also be used inconfigurable RS pattern, which may include at least one of a referencesignal density configuration in time domain, a reference signal densityconfiguration in frequency domain and a reference signal frequencyoffset configuration. In such a case, it will be advantageous if thecommon reference signal sequence is generated further based on a wholeset of resource elements used for RS transmission in different referencesignal configurations.

As illustrated in FIG. 9, the RS pattern is nested in time-frequencydomain and if the configurable RS pattern is supported in NR system,there might be various RS patterns, those with different offsets, withdifferent densities, with/without additional transmission, etc., asthose illustrated in right figure in FIG. 9. In such a case, it mayobtain a whole set of resource elements used for RS transmission indifferent RS configurations as illustrated in the left figure in FIG. 9,and thus REs and modulated symbols on related REs can all be selectedfrom the whole set. Then, it is possible to generate a common RSsequence further based on a whole set of resource elements used for RStransmission in different reference signal configurations. Accordingly,a RS sequence for a RS pattern of a terminal device can be obtained fromthe common RS sequence.

With the common RS sequence generated based on the whole set of resourceelements used for RS transmission in different reference signal patternconfigurations, for UE with different RS patterns such as differentdensities, their respective RS sequences will be obtained the common RSsequence.

FIG. 10 schematically illustrates a common RS sequence and RS sequencesfor respective UE with different RS densities according to an embodimentof the present disclosure. As illustrated, the common RS sequence has alength M, thus the sequence can be represented by R_i, i=0, 1, . . . ,M−1. For UE configured with different densities, the densityconfiguration can be informed to the UE. For different densityconfigurations, UE can abstract the needed sequence from the commonsequence R_i. For example, for UE with a density of 1, the sequencetherefor is R_i, i=0, 1, . . . , M−1, while for UE with a density of ½,the sequence thereof is R_i, i=0, 2, 4 . . . 2·└(M−1)/2┘, or R_i, i=1,3, 5 . . . .

Similarly, for different SCS configurations, UE can also abstract theneeded sequence from the common sequence.

For example, the UE with maximum density or minimum SCS k₀, the sequenceis R_i, i=0, 1, . . . , M−1; while for UE with density 1/K or SCS K*k₀,the sequence can be expressed as

R_i,i=i _(start) ,i _(start) ,+K+o,i _(start)+2·K+o, . . . ,i_(start)+1·K+o,i _(end)1=0,1,2

where i_start is the start index of the sequence, i_end is the end indexof the sequence, K is parameter of density (for ½ density configuration,K=2), or parameter of SCS (K·k₀, wherein the reference SCS is k₀), o isoffset configuration. These parameters can be configured separately ortogether. The reference SCS k₀ can be configured by network. Forexample, for some network, the reference SCS is 15 kHz, 30 kHz, 60 kHz,120 kHz or 240 kHz.

In an embodiment of the present disclosure, for different symbol/slots,the RS sequence can be same or generated with different initial values.

In another embodiment of the present disclosure, the RS sequence can begenerated for a time-frequency region. The reference density in one PRBin frequency domain can be denoted by do (e.g. maximum density), thereference SCS can be denoted by k₀ (e.g. minimum SCS), the referencedensity in time domain can be denoted by to (e.g. maximum density), thenumber of PRB (with reference SCS k₀) can be denoted by N, the length inone symbol in the whole bandwidth can be denoted by L (e.g. L=N*d₀), andthe maximum length of the sequence can be denoted by M (e.g. M=L*t₀).The common sequence is R_i, i=0, 1, . . . , M−1. For UE with differentconfigurations, it can abstract needed sequence from the common RSsequence.

For UE configured with different SCS ki, its RS sequence can beabstracted every ki/k₀, similar to the case as illustrated in FIG. 10.For UE configured with different densities di in frequency domain, itsRS sequence can be abstracted from the common RS sequence every di/do,also similar to the case as illustrated in FIG. 10. For UE configuredwith different time densities ti, its RS sequence can be abstracted froma RS sequence group, as illustrated in FIG. 11. For UE configured withdifferent patterns, its RS sequence can be just abstracted from thecommon RS sequence accordingly.

For UE configured with different patterns in time domain and differentband allocations in frequency domain, their respective RS sequences canbe just abstracted from the common RS sequence corresponding to theirband allocations and their RS patterns as illustrated in FIG. 12.

In an embodiment of the present disclosure, RS modulated symbols in onesymbol and one PRB can be similar and then the RS sequence for UE withdifferent densities in frequency domain can be easily obtained.

In another embodiment of the present disclosure, modulated symbols inthe common reference signal sequence vary by any of: a time-frequencyblock; a predetermined number of subcarriers in frequency domain; and apredetermined number symbols in time domain.

As illustrated in FIG. 13, the modulated symbols in the common RSsequence can vary by a predetermined number of subcarriers in thefrequency domain. That is to say, within these subcarriers, modulatedsymbols can be same but may be different from modulated symbols inanother predetermined number of subcarriers.

As an alternative, as illustrated in FIG. 14, modulated symbols in thecommon RS sequence can vary by a predetermined number of symbols in thetime domain. That is to say, modulated symbols in the predeterminednumber of symbols will be same but may be different from anotherpredetermined number of symbols.

In addition, modulated symbols in the common RS sequence can also varyby a time-frequency block, as illustrated in FIG. 15. That is to say,within the same time-frequency block, modulated symbols will be same butdifferent from another time-frequency blocks. The time-frequency blocksmay have no frequency shift there between as illustrated at left side inFIG. 15 or have a predetermined frequency shift as illustrated at rightside in FIG. 15.

In addition, the density for one RS in different symbols can bedifferent as illustrated in FIG. 16A (with no offset) and FIG. 16B (withoffest). In such a case, there might be several options. In the firstoption, the RS sequence may be generated for the first symbol containingRS, and the modulated symbols in following symbols can be generatedbased on the first one in the same frequency position. for example aresame as or multiplied by a frequency offset (a complex value) with thefirst one in the same frequency position. In a second option, one commonRS sequence is generated for a time-frequency block, and modulatedsymbols on different symbols can be abstracted from the common RSsequence. In a third option, it may initialize the RS sequence for eachsymbol.

In NR system, phase tracking RS (PT-RS) is introduced, which is areference signal used for tracking phase noise or frequency offset andwere agreed in RAN1 #87 meeting. According to the agreement in RAN1 #87meeting, the density of PT-RS in frequency domain can be rather spare.In such a case, the sequence of PT-RS can be generated based on aprevious DMRS in the same frequency position. That is to say, the PT-RSmay be same as or multiplied with frequency offset (a complex value)with the previous DMRS in the same frequency position. Alternatively, itis also possible to generate the sequence of the PT-RS with configuredsequence index and in such a case, the sequence configurationinformation can be transmitted to the terminal device.

Hereinbefore, description is made to operations related to the new RSsolution at network side. Hereinafter, reference will be made to FIG. 17to describe operations related to the new RS solution at terminal deviceside.

FIG. 17 further schematically illustrates a flow chart of method forreference signal receiving according to an example embodiment of thepresent disclosure. The method 1700 can be implemented at a terminaldevice, for example UE, or other like terminal devices.

As illustrated in FIG. 17, the method starts from step 1701, in whichthe terminal device like UE receives a reference signal sequencetransmitted from network side and sequence configuration informationindicating a parameter by which a reference signal sequence transmittedfor the terminal device can be obtained.

In an embodiment of the present disclosure, the sequence configurationinformation can be explicit information which, for example, may comprisesequence position information indicating a position at which thereference signal sequence for the terminal device is located in thecommon reference signal sequence. As an example, the sequence positioninformation may comprise any of: a start index and an end index of thereference signal sequence for the terminal device; a start index and thelength of the reference signal sequence for the terminal device; an endindex and the length of the reference signal sequence for the terminaldevice an offset value relative to the frequency configuration of theterminal device; and an offset value relative to a fixed frequencyposition.

In another embodiment of the present disclosure, the sequenceconfiguration information can be implicit information which is, forexample, indicated by other parameters including any of:boundaries/length of frequency band allocated to the terminal device;frequency band configuration of the terminal device; and a sequencegeneration initial value for the terminal device.

Next, at step 1702, an initial reference signal sequence for theterminal device can be obtained based on the sequence configurationinformation. At the terminal device, the terminal device may generatethe common RS sequence in a similar way as those described withreference to FIGS. 4 to 16. Accordingly, the terminal device canabstract its initial RS sequence based on the sequence configurationinformation received in step 1702. Thus, the terminal device can knowthe initial RS sequence which does not undergo the channel between theserving node such as node B and the terminal device such as UE. By meansof the initial RS sequence and the RS sequence that the terminal deviceat its allocated frequency band in step 702, it is possible to forexample perform channel estimation or co-scheduling.

In an embodiment of the present disclosure, the obtaining the initialreference signal sequence for the terminal device may include obtainingthe initial reference signal sequence for the terminal device based onthe sequence configuration information and reference signal pattern forthe terminal device. The reference signal pattern may include at leastone of a reference signal density configuration in time domain, areference signal density configuration in frequency domain and areference signal frequency offset configuration.

Thus, with embodiments of the present disclosure, a reference signalsequence solution with a low complexity is proposed for the wirelesscommunication system (especially for new radio access system) withdynamic bandwidth allocation and/or configurable reference signalpattern, wherein one common reference signal sequence can be generatedand shared by at least some of terminal devices, irrespective ofreference signal transmission configurations like bandwidth allocationand/or reference signal pattern configurations. Thus, it is possible toperform RS measurement and multi-user scheduling for UE even if they areconfigured different bandwidth allocation and/or configurable referencesignal pattern. In addition, it can achieve better interferencecancellation since reference signals from interfering cells will be easyto be obtained. Moreover, it only needs terminal devices to generate few(e.g. only one) common reference signal sequence for different bandallocations and/or RS pattern configurations, which means a less complexsolution.

Besides, in the present disclosure, there are also provided apparatusesfor reference signal transmission and receiving at the serving node andterminal device in a wireless communication system respectively, whichwill be described next with reference to FIGS. 18 and 19.

FIG. 18 schematically illustrates a block diagram of an apparatus 1800for reference signal transmission in a wireless communication systemaccording to an embodiment of the present disclosure. The apparatus 1800can be implemented at a serving node, for example a BS, like a node B(NodeB or NB).

As illustrated in FIG. 18, the apparatus 1800 may comprise a referencesignal generation module 1801 and a sequence and informationtransmission module 1802. The reference signal generation module 1801may be configured to generate, based on a frequency range configurationat network side, a common reference signal sequence shared by at leastsome of terminal devices respectively allocated with their own referencesignal transmission configurations. The sequence and informationtransmission module 1802 may be configured to transmit the commonreference signal sequence and sequence configuration information to aterminal device, the sequence configuration information indicating aparameter by which a reference signal sequence transmitted for theterminal device can be obtained.

In an embodiment of the present disclosure, the sequence configurationinformation may comprise sequence position information indicating aposition at which the reference signal sequence for the terminal deviceis located in the common reference signal sequence.

In another embodiment of the present disclosure, the sequence positioninformation may comprise any of: a start index and an end index of thereference signal sequence for the terminal device; a start index and thelength of the reference signal sequence for the terminal device; an endindex and the length of the reference signal sequence for the terminaldevice; an offset value relative to the frequency configuration of theterminal device and an offset value relative to a fixed frequencyposition.

In a further embodiment of the present disclosure, the sequenceconfiguration information can be indicated by any of: boundaries/lengthof frequency band allocated to the terminal device; frequency bandconfiguration of the terminal device; and a sequence generation initialvalue for the terminal device.

In a still further embodiment of the present disclosure, the frequencyrange configuration at network side may comprise any of the systembandwidth; and the frequency band configured for a node serving theterminal device.

In a yet further embodiment of the present disclosure, the referencesignal transmission configurations comprise at least one of: bandwidthallocation; and a reference signal density configuration in time domain;reference signal density configuration in frequency domain; and areference signal frequency offset configuration.

In another embodiment of the present disclosure, the reference signalgeneration module 1801 may be further configured to generate, fordifferent frequency range configurations, the common reference signalsequence based on a frequency range covering all possible frequencyranges of the different frequency range configurations. The differentfrequency range configurations may have at least one of differentsubcarrier spacing configurations and different cyclic prefixconfigurations.

In a further embodiment of the present disclosure, the reference signalgeneration module 1801 may be further configured to generate the commonreference signal sequence further based on a whole set of resourceelements used for RS transmission in different reference signalconfigurations.

In a still further embodiment of the present disclosure, modulatedsymbols in the common reference signal sequence may vary by any of: atime-frequency block; a predetermined number of subcarriers in frequencydomain; and a predetermined number symbols in time domain.

In a yet further embodiment of the present disclosure, modulated symbolsin a reference signal sequence in a symbol may be generated based onthose in a reference signal sequence in a previous symbol in a samefrequency position.

In another embodiment of the present disclosure, the reference signalsequence in the symbol may have at least one of different densities anddifferent frequency offsets from the reference signal sequence in theprevious symbol.

FIG. 19 further schematically illustrates a block diagram of anapparatus 1900 for reference signal receiving in a wirelesscommunication system according to an embodiment of the presentdisclosure. The apparatus 1900 can be implemented at a terminal device,for example UE, or other like terminal devices.

As illustrated in FIG. 19, the apparatus 1900 may include a sequence andsignal receiving module 1901 and a sequence obtainment module 1902. Thesignal receiving module 1901 can be configured to receive a referencesignal sequence transmitted from network side and sequence configurationinformation indicating a parameter by which a reference signal sequencetransmitted for the terminal device can be obtained. The sequenceobtainment module 1902 can be configured to obtain an initial referencesignal sequence for the terminal device based on the sequenceconfiguration information.

In an embodiment of the present disclosure, the sequence obtainmentmodule 1902 may be further configured to: obtain the initial referencesignal sequence for the terminal device based on the sequenceconfiguration information and reference signal pattern for the terminaldevice.

Hereinbefore, the apparatuses 1800 and 1900 are described with referenceto FIGS. 18 and 19. It is noted that the apparatuses 1800 and 1900 maybe configured to implement functionalities as described with referenceto FIGS. 4 to 17. Therefore, for details about the operations of modulesin these apparatuses, one may refer to those descriptions made withrespect to the respective steps of the methods with reference to FIGS. 4to 17.

It is further noted that the components of the apparatuses 1800 and 1900may be embodied in hardware, software, firmware, and/or any combinationthereof. For example, the components of apparatuses 1800 and 1900 may berespectively implemented by a circuit, a processor or any otherappropriate selection device.

Those skilled in the art will appreciate that the aforesaid examples areonly for illustration not limitation and the present disclosure is notlimited thereto; one can readily conceive many variations, additions,deletions and modifications from the teaching provided herein and allthese variations, additions, deletions and modifications fall theprotection scope of the present disclosure.

In addition, in some embodiment of the present disclosure, each ofapparatuses 1800 and 1900 may comprise at least one processor. The atleast one processor suitable for use with embodiments of the presentdisclosure may include, by way of example, both general and specialpurpose processors already known or developed in the future. Each ofapparatuses 1800 and 1900 may further comprise at least one memory. Theat least one memory may include, for example, semiconductor memorydevices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The atleast one memory may be used to store program of computer executableinstructions. The program can be written in any high-level and/orlow-level compliable or interpretable programming languages. Inaccordance with embodiments, the computer executable instructions may beconfigured, with the at least one processor, to cause apparatuses 1800and 1900 to at least perform operations according to the method asdiscussed with reference to FIGS. 4 to 17 respectively.

FIG. 20 further illustrates a simplified block diagram of an apparatus2010 that may be embodied as or comprised in a serving node like a basestation in a wireless network and an apparatus 2020 that may be embodiedas or comprised in a terminal device like UE as described herein.

The apparatus 2010 comprises at least one processor 2011, such as a dataprocessor (DP) and at least one memory (MEM) 2012 coupled to theprocessor 2011. The apparatus 2010 may further comprise a transmitter TXand receiver RX 2013 coupled to the processor 2011, which may beoperable to communicatively connect to the apparatus 2020. The MEM 2012stores a program (PROG) 2014. The PROG 2014 may include instructionsthat, when executed on the associated processor 2011, enable theapparatus 2010 to operate in accordance with embodiments of the presentdisclosure, for example the method 400. A combination of the at leastone processor 2011 and the at least one MEM 2012 may form processingmeans 2015 adapted to implement various embodiments of the presentdisclosure.

The apparatus 2020 comprises at least one processor 2021, such as a DP,and at least one MEM 2022 coupled to the processor 2021. The apparatus2020 may further comprise a suitable TX/RX 2023 coupled to the processor2021, which may be operable for wireless communication with theapparatus 2010. The MEM 2022 stores a PROG 2024. The PROG 2024 mayinclude instructions that, when executed on the associated processor2021, enable the apparatus 2020 to operate in accordance with theembodiments of the present disclosure, for example to perform the method1700. A combination of the at least one processor 2021 and the at leastone MEM 2022 may form processing means 2025 adapted to implement variousembodiments of the present disclosure.

Various embodiments of the present disclosure may be implemented bycomputer program executable by one or more of the processors 2011, 2021,software, firmware, hardware or in a combination thereof.

The MEMs 2012 and 2022 may be of any type suitable to the localtechnical environment and may be implemented using any suitable datastorage technology, such as semiconductor based memory devices, magneticmemory devices and systems, optical memory devices and systems, fixedmemory and removable memory, as non-limiting examples.

The processors 2011 and 2021 may be of any type suitable to the localtechnical environment, and may include one or more of general purposecomputers, special purpose computers, microprocessors, digital signalprocessors DSPs and processors based on multicore processorarchitecture, as non-limiting examples.

In addition, the present disclosure may also provide a carriercontaining the computer program as mentioned above, wherein the carrieris one of an electronic signal, optical signal, radio signal, orcomputer readable storage medium. The computer readable storage mediumcan be, for example, an optical compact disk or an electronic memorydevice like a RAM (random access memory), a ROM (read only memory),Flash memory, magnetic tape, CD-ROM, DVD, Blue-ray disc and the like.

The techniques described herein may be implemented by various means sothat an apparatus implementing one or more functions of a correspondingapparatus described with one embodiment comprises not only prior artmeans, but also means for implementing the one or more functions of thecorresponding apparatus described with the embodiment and it maycomprise separate means for each separate function, or means that may beconfigured to perform two or more functions. For example, thesetechniques may be implemented in hardware (one or more apparatuses),firmware (one or more apparatuses), software (one or more modules), orcombinations thereof. For a firmware or software, implementation may bemade through modules (e.g., procedures, functions, and so on) thatperform the functions described herein.

Exemplary embodiments herein have been described above with reference toblock diagrams and flowchart illustrations of methods and apparatuses.It will be understood that each block of the block diagrams andflowchart illustrations, and combinations of blocks in the blockdiagrams and flowchart illustrations, respectively, can be implementedby various means including computer program instructions. These computerprogram instructions may be loaded onto a general purpose computer,special purpose computer, or other programmable data processingapparatus to produce a machine, such that the instructions which executeon the computer or other programmable data processing apparatus createmeans for implementing the functions specified in the flowchart block orblocks.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyimplementation or of what may be claimed, but rather as descriptions offeatures that may be specific to particular embodiments of particularimplementations. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub-combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or variation of a sub-combination.

It will be obvious to a person skilled in the art that, as thetechnology advances, the inventive concept can be implemented in variousways. The above described embodiments are given for describing ratherthan limiting the disclosure, and it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit and scope of the disclosure as those skilled in the artreadily understand. Such modifications and variations are considered tobe within the scope of the disclosure and the appended claims. Theprotection scope of the disclosure is defined by the accompanyingclaims.

1. A method of a User Equipment (UE), the method comprising: generatinga first sequence, for a Channel State Information Reference Signal(CSI-RS); and receiving the CSI-RS at second positions, wherein thefirst sequence is mapped to a resource for the CSI-RS, the resource isconfigured within a UE-specific bandwidth, a UE-specific bandwidth is apart of a cell-specific bandwidth of a cell, the first sequence has atleast two elements, each of the at least two elements has a respectiveindex, each respective index is associated with a different one ofrespective indexes of the second positions on the resource, therespective indexes of the second positions is defined relative to acell-specific position in a frequency domain, the cell-specific positionis common for each UE within the cell, the UE is capable of beingscheduled within the UE-specific bandwidth, a plurality of UEs arewithin the cell, and each one of the plurality of UEs within the cellhas a different UE-specific bandwidth.
 2. The method according to claim1, wherein the UE-specific bandwidth may overlap in the frequency domainwith a UE-specific bandwidth configured for other UEs.
 3. The methodaccording to claim 1, wherein the first sequence corresponds to theUE-specific bandwidth.
 4. A method of a base station, the methodcomprising: generating a first sequence, for a Channel State InformationReference Signal (CSI-RS); and transmitting the CSI-RS at secondpositions, wherein the first sequence is mapped to a resource for theCSI-RS, the resource is configured within a UE-specific bandwidth, aUE-specific bandwidth is a part of a cell-specific bandwidth of a cell,the first sequence has at least two elements, each of the at least twoelements has a respective index, each respective index is associatedwith a different one of respective indexes of the second positions onthe resource, the respective indexes of the second positions is definedrelative to a cell-specific position in a frequency domain, thecell-specific position is common for each UE within the cell, the basestation is capable of performing scheduling within the UE-specificbandwidth, a plurality of UEs are within the cell, and each one of theplurality of UEs within the cell has a different UE-specific bandwidth.5. The method according to claim 4, wherein the UE-specific bandwidthmay overlap in the frequency domain with a UE-specific bandwidthconfigured for other UEs.
 6. The method according to claim 4, whereinthe first sequence corresponds to the UE-specific bandwidth.
 7. A UserEquipment (UE), comprising a processor configured to: generate a firstsequence, for a Channel State Information Reference Signal (CSI-RS); andreceive the CSI-RS at second positions, wherein the first sequence ismapped to a resource for the CSI-RS, the resource is configured within aUE-specific bandwidth, a UE-specific bandwidth is a part of acell-specific bandwidth of a cell, the first sequence has at least twoelements, each of the at least two elements has a respective index, eachrespective index is associated with a different one of respectiveindexes of the second positions on the resource, the respective indexesof the second positions is defined relative to a cell-specific positionin a frequency domain, the cell-specific position is common for each UEwithin the cell, the UE is capable of being scheduled within theUE-specific bandwidth, a plurality of UEs are within the cell, and eachone of the plurality of UEs within the cell has a different UE-specificbandwidth.
 8. The UE according to claim 7, wherein the UE-specificbandwidth may overlap in the frequency domain with a UE-specificbandwidth configured for other UEs.
 9. The UE according to claim 7,wherein the first sequence corresponds to the UE-specific bandwidth. 10.A base station comprising a processor configured to: generate a firstsequence, for a Channel State Information Reference Signal (CSI-RS); andtransmit the CSI-RS at second positions, wherein the first sequence ismapped to a resource for the CSI-RS, the resource is configured within aUE-specific bandwidth, a UE-specific bandwidth is a part of acell-specific bandwidth of a cell, the first sequence has at least twoelements, each of the at least two elements has a respective index, eachrespective index is associated with a different one of respectiveindexes of the second positions on the resource, the respective indexesof the second positions is defined relative to a cell-specific positionin a frequency domain, the cell-specific position is common for each UEwithin the cell, the base station is capable of performing schedulingwithin the UE-specific bandwidth, a plurality of UEs are within thecell, and each one of the plurality of UEs within the cell has adifferent UE-specific bandwidth.
 11. The base station according to claim10, wherein the UE-specific bandwidth may overlap in the frequencydomain with a UE-specific bandwidth configured for other UEs.
 12. Thebase station according to claim 10, wherein the first sequencecorresponds to the UE-specific bandwidth.